Why so many JL Audio Fathom subs for sale I wonder

Just mulling some thoughts around about JL Audio subwoofers. Been thinking of adding one, maybe 2 to my system. They are awesome subs and come highly reviewed in the Absolute Sound, and Stereophile. Recommended components, powerful as hell, accurate, flexible...all very positive attributes. I have a few friends that own F112's, F113's.
So why do so many of them show up for sale here on A-gon? I'de like to get some input from A-gon members as to why that might be? Seems baffling that something so highly regarded and affordable ends up for sale so often. Thoughts anyone?
When I heard a single JL in an extreme high end 2 channel system I was very impressed. Sounded like the real thing, very, very good sub. I would not worry that they show up used!
Subs sound incredible if placed center between the 2 mains. Not only because it is more smooth, but because phase can be dialed spot on.

Move your equipment to the coner, put the sub under the TV. Then you will love your sub.
To its ability to output well defined extra low frequency the JL can do an outstanding job. I've heard their technical support can be very helpful. The JL Audio Automatic Room Optimization is very useable but may need updating. The JLs brut force paired with an Audyssey system or similar, would make it a contemporary world class performer.

Understandably, the failure to successfully integrate a subwoofer by selecting a favorite recording with deep bass content and simply adjusting the crossover, volume, and location is stunningly outmoded.

I've been in many post production studios and all of them use a sub/s. With decent low frequency room equalization almost any subwoofer can be a useful addition to almost any system IMO.
Well you know what? You've all convinced me that buying a JL Audio sub , maybe 2, is going to be ok. This is great to hear, and everybody who's contributed to this thread has made alot of sense, so thank you all for your input. I think I'll just snap me up a Fathom F113 and give it a spin in my listening room. Or would anyone suggest I buy an Fathom F212?? My listening room is approx. 15 feet wide x 18 feet deep with 9 foot ceilings. I'm running MBL 101e Mk2's with MBL 9008A's and a MBL 6010D. Already a pretty potent match, and when I run my JM Lab / Focal sub...the result is quite good. Actually it's DAMN good (not to sound like a braggart or anything). If I step up to a single Fathom F113 do any of you think that would be "sufficient" given my room dimensions? I wouldn't be looking to use the JM Lab /Focal sub in the mix any longer. Just a single (maybe a pair?) of F113's. Or just a single F212. Again, as mentioned in my original posting, I'm a bass freak. So it absolutely MUST play clean, tight, loud as hell, and hit like a sledgehammer. The JM Lab / Focal I have IS all that...but only to a point. I'm looking for "bone-crushing" bass. (Yeah, I'll admit it. I'm into ROCK, and Heavy Metal, hence MBL speakers, amps, and Preamp.) That having been said- and given my room dimensions- what would YOU folks do with regard to my quest for monster, ass-kicking bass?? 1? a pair? Like to see where others would go with this. Thanks in advance for humoring me about this.